Each other's identity! :)

Light and dark
High and low
Deep and shallow
Success and failure
Selection and rejection
Joys and tears
Life and death
Are antonyms
Yet they are
An inevitable
Part of
Each other's
IDENTITY.
They cannot
Exist simultaneously
Yet they are
Inseparable
From each other's
IDENTITY.
They define
Each other's
Importance
Relevance
And
Necessity